Friday 16 February 2001 05.16 EST
First published on Friday 16 February 2001 05.16 EST

The Guardian will make legal history today when it launches a high court challenge under the Human Rights Act to a 153-year-old law which threatens anyone calling in print for abolition of the monarchy with life imprisonment.

The Guardian's editor, Alan Rusbridger, and columnist Polly Toynbee will file a claim at the high court in London today against the attorney general, Lord Williams of Mostyn, and the director of public prosecutions, David Calvert-Smith.

The case is the first to be brought purely under the Human Rights Act since it came into force last October. The act has been invoked in criminal and civil cases but the Guardian's is the first to be brought under a freestanding right to bring proceedings in a court or tribunal.

The claim alleges that the 1848 Treason Felony Act violates article 10 of the European Convention on Human Rights, which guarantees the right to free speech.

The paper launched a campaign last December 6 - the date of the Queen's speech at the state opening of parliament - urging readers to support moves to establish Britain as a republic. The editor contacted the attorney general before publication seeking assurances that he and his staff would not be prosecuted if they advocated change by peaceful means only.

Lord Williams replied that such conduct "may be criminal" and refused to confirm that there would be no prosecution. None of the journalists who called for a republic has been threatened with prosecution. But the December 6 edition is still available as a back issue, the articles can be downloaded from the Guardian website, and the paper plans to continue its campaign.

"It is of importance to the right of freedom of expression guaranteed to the claimants and to their readers that the threat to prosecute should be authoritatively declared either baseless or real," papers filed with the court say.

The Guardian is seeking to clarify the Treason Felony Act as the first step in a legal campaign which will see it backing a challenge the Act of Settlement, the 300-year-old law which bans non-Protestants from succession to the British throne and discriminates against women and those born out of wedlock.

Mr Rusbridger said: "The Treason Felony Act is one more piece of archaic legal nonsense surrounding the monarchy. People may say it's meaningless but meaningless laws are bad laws. Like the Act of Settlement, it's about time it was scrapped."

He and Ms Toynbee are asking the court to interpret the Treason Felony Act to mean that advocating the overthrow of the monarchy by non-violent methods is no longer a crime. Under the Human Rights Act, judges have power to amend the wording of acts of parliament to make them comply with rights guaranteed by the European Convention.

If this is impossible, they may declare the statute incompatible, leaving it to parliament to amend it or face proceedings at the European Court of Human Rights in Strasbourg.